Does linux Need Defrag?

[irne.barnard]

I don't think this has been mentioned yet but using Tranmission (bittorrent) to download files can cause severe filesystem fragmentation at least on ext3. Severe to the point you can't burn a cd iso on a drive that can do 120MB/s sequential without first defragmenting the file. ext4 is supposed to be a bit better about fragmentation problems due to having prealloc. However even it is not perfect and tytso is working on an ext4 defrag utility.

filefrag (filename) will tell you how many extents are in your file and thus to what extent a particular file is fragmented. I don't know if there is a tool that will tell you this for the whole filesystem, but I think fsck might tell you at the end of a run.

That's very similar to the problems with databases. It's a large file which gets added to over time. Thus a contiguous space is allocated to it, but once it grows larger a new fragment is created.

Not using torrents, I'm not sure if there's one which would work the following way. Most of the download managers first create a file of the size they're downloading. The content is garble at first, which simply gets filled in as more data is downloaded. This way fragmentation is kept to a minimum in this case. Maybe there's a torrent client which does the same?

[irne.barnard]

A very interesting thread, some different points of view, so what is the answer should people reinstall their OS,s from time to time.

Only if you want to. It should be sufficient to remove old files (which you don't need anymore) - of course after backup / archive

Only in the "strange" cases would fragmentation become a problem. Unfortunately you do find some programs which use database like files, and then they don't follow the previously mentioned database pre-allocated file method. One I found cause enormous amounts of fragmentation on Windows is Revit. These files tend to grow (over time) from 50k to 200MB+. I've not tried them on Ubuntu yet, as it doesn't work under Wine.

[calc]

Here is a new comment by Theodore Ts'o about the status of e2defrag.

https://bugs.launchpad.net/ubuntu/+b...28/comments/22